Standard proof environment \begin{proof}[source] ... \end{proof} with
halmos at end

Algorithm environments

\bibalias{foo}{bar} makes \cite{foo} act like \cite{bar}.
Useful with large bibliographies like geombib.

Lots of other
TEX hax.

jeffeproc.sty:
Package for two-column proceedings papers. Unlike similar
packages from ACM and SIAM, this one actually works! Margins
set according to ACM/IEEE/SIAM guidelines; other space
parameters smaller than standard latex. Optional 1 inch space
below first column for publisher-supplied copyright notice.
Options for ACM- or SIAM-style section headers. Options to
set bibliography in smaller type.

Removes any limitation on the number of authors that can
appear on the title page. (ACM imposes a hard-wired limit
of three authors. No, really.)

Removes all hardwired Times and Helvetica fonts, except
in the required copyright
statement and
optionally in the title, authors, and affiliations.
(Some HaXing is still required to make that look good,
but that should be fixed Real Soon Now).

Makes footnotes smaller than normal text (but not smaller
than small text)

I recommend using jeffe.sty to
redefine ACM's ugly captions, theorems, and proofs.
Imminentize the eschaton at your own risk!

myconcrete.sty:
Use the Concrete Math text fonts. Especially useful with
euler.sty, which sets up the AMS
Euler math fonts. Unfortunately, this style only works with
the type-3 concrete fonts available with most standard TeX
distributions, so you can't use it with pdflatex. (Type-1
versions of these fonts are available as part of the
CM-Super font package, but this package is not
compatible with them.)

scribe.sty:
Package for scribe notes, loosely based on the MIT/Berkeley
scribe note style but rewritten from scratch. Here are some sample scribe notes (and
their latex source), which
reveal the secret origin of the typesetter's chant: Lorem
isum dolor sit amet...

abuser.bst:
BibTeX style mostly stolen from David Eppstein. Supports the
url field, with angle brackets as per AMA guidelines. Works
around geom.bib's confusion about volume and number for
proceedings papers. Requires url.sty.